Numerous tire pressure monitoring systems have been developed in order to detect when the air pressure within a tire drops below a threshold pressure value. A system typically includes a pressure switch, an internal power source, and a communications link that provides the tire pressure information from a location at each vehicle tire to a central receiver, which may be mounted on the vehicle dashboard. The communications link may be a wired or wireless link.
There has been an increasing need for tire pressure monitoring systems due to the use of "run flat" tires in vehicles. The "run flat" tires enable a driver to travel an extended distance after the loss of air pressure within a vehicle tire.
As more vehicles are equipped with tire pressure sensing systems, steps must be taken to reduce the likelihood of overlapping signals from tire pressure sensing modules. Examples of tire pressure monitoring systems are disclosed in U.S. Pat. No. 4,316,176, U.S. Pat. No. 5,573,610, U.S. Pat. No. 5,600,301, U.S. Pat. No. 5,602,524, U.S. Pat. No. 5,612,671 and U.S. Pat. No. 5,656,993.